This work investigates the interaction between pulsed excimer laser-induced plasma and an excimer laser beam. The optical transmissivity through the laser-induced plasma and the velocity of the plasma front are measured within the duration of the laser pulse. Based on the measured velocity of the plasma front, an analysis of compressible gas dynamics is used to compute the thermodynamic properties of the plasma layer, including temperature, pressure, and the number density of the laser-evaporated particles. The absorption coefficient of each absorption mode in the plasma is then calculated from the thermodynamic properties. By comparing the calculated and the measured transmissivity of the laser-induced plasma, we have determined the dominant absorption mechanism in the plasma plume to be photo-ionization at laser intensities in the range 90-400 MW/cm2.